Pulse combustors have been known for many years. They work on the principle that a load of mixed fuel and air periodically enters a combustion chamber where it ignites, therefore giving a pulse combustion. Some pulse combustors are specifically adapted for use as burners. Other pulse combustors are specifically adapted for use as engines of the pulse-jet type. Typical pulse-jet engines use valves which periodically allow fuel and air intake. There is a general need in the field of pulse combustors to enhance efficiency, durability and thrust output of pulse combustors.
U.S. Pat. No. 3,093,962 to Gluhareff teaches a valveless pulse-jet engine and somewhat discusses the use of acoustics. There is a need in the art to somewhat elaborate on the teachings of Gluhareff.
Furthermore, known pulse combustors are typically limited to a pulse mode of combustion.
An aim of the improvements is to alleviate some of the needs concerning combustors.
In accordance with one aspect, the improvements provide an ejector system comprising: a supersonic fluid injection nozzle having an acoustic injection frequency and amplitude; a first resonant tube having an inlet coupled to the nozzle for receiving the injected fluid from the nozzle and ambient fluid entrained by the injected fluid, and an outlet for ejecting the fluids, the first resonant tube having a first fundamental resonance frequency excitable by the nozzle injection; and a second resonant tube having an inlet coupled to receive the fluids ejected from the outlet of the first resonant tube outlet for receiving the ejected fluids and additional ambient fluid entrained by the ejected fluids, and an outlet for ejecting the fluids received by the inlet, the second resonant tube having a second fundamental resonance frequency being a sub-harmonic of the first fundamental resonance frequency.
In accordance with an other aspect, the improvements provide an ejector system having a first resonant tube having a first fundamental resonance frequency, an inlet and an outlet, a second resonant tube wider than the first resonant tube having a second fundamental resonance frequency, an inlet coupled to the outlet of the first resonant tube, and an outlet, and a supersonic fluid nozzle aerodynamically coupled to the inlet of the first resonant tube, the supersonic fluid nozzle having an acoustic injection frequency and amplitude suitable to acoustically excite the first and the second resonant tubes, the ejector system being CHARACTERIZED IN THAT the first resonance frequency is a harmonic of the second resonance frequency.
In accordance with an other aspect, the improvements provide an intake system for a combustor having a pulsating frequency, the intake system comprising: a supersonic injection fuel nozzle having an acoustic injection frequency and amplitude; a first resonant tube having an inlet coupled to the nozzle for receiving the injected fuel and ambient air entrained by the injected fuel, and an outlet for ejecting the fuel and the air, the first resonant tube having a first fundamental resonance frequency excitable by the fuel nozzle; a second resonant tube having an inlet coupled to the outlet of the first resonant tube for receiving the ejected fuel and air and additional ambient air entrained by the ejected fuel and air, and an outlet, the second resonant tube having a second fundamental resonance frequency being a sub-harmonic of the first fundamental resonance frequency; and a resonant intake tube having an inlet coupled to the outlet of the second resonant tube for receiving the fluids ejected from the second resonant tube outlet and additional ambient fluid entrained by these ejected fluids, and an outlet connected to a combustion chamber inlet of the combustor.
In some cases, the combustor further has a resonator having a fundamental resonance frequency which corresponds to the pulsating frequency, the resonator further having the combustion chamber inlet, an outlet, an oscillator for use as the combustion chamber, having the inlet at an acoustic center thereof and defining one end of the resonator, and an exhaust pipe extending from the oscillator and having the outlet at the opposite end of the resonator, wherein the oscillator has a resonance frequency which is an odd harmonic of the pulsating frequency and at least one of the coupling between the first resonant tube and the second resonant tube and the coupling between the second resonant tube and the intake tube has a difference of area and a penetration depth suitable for the intake system to define a high-pass filter having a cut-off frequency between the pulsating frequency and the oscillator fundamental frequency.
In some cases, the odd harmonic is the third harmonic.
In accordance with an other aspect, the improvements provide a method of ejecting fluid, the method comprising: making high frequency noise by injecting one of an over-expanded and under-expanded supersonic flow of fluid into a first resonant tube at a speed sufficient for the fluid momentum to entrain ambient fluid through the first tube, and for the fluid exiting the first tube to entrain further air particles through a second tube; and driving the first tube into resonance using the high frequency noise, and driving the second tube into resonance using the resonance of the first tube.
In some cases, the ejected fluid is fuel and the ambient fluid is air.
In accordance with an other aspect, the improvements provide an acoustic cavity for use in a combustor having a pulsating frequency, the acoustic cavity comprising: a resonator with a fundamental resonance frequency which corresponds to the pulsating frequency of the combustor, the resonator further having an inlet, and an outlet; an oscillator made integral to the resonator and defining one end thereof, being for use as a combustion chamber, having a fundamental resonance frequency which is an odd harmonic of the pulsating frequency and having the inlet at an acoustic center thereof, and an exhaust pipe made integral to the resonator and having the outlet at an opposite end thereof, the exhaust pipe extending from the oscillator.
In accordance with an other aspect, the improvements provide a combustor comprising: a resonator having a fundamental resonance frequency which corresponds to a pulsating frequency of the combustor when operating in a pulse mode, the resonator further having: an oscillator for use as a combustion chamber, having a fundamental resonance frequency which is an odd harmonic of the pulsating frequency, and having an inlet at an acoustic center thereof, the oscillator defining one end of the resonator, and an exhaust pipe extending from the oscillator and having an outlet at the opposite end of the resonator; and an intake system connected to the inlet to feed the combustion chamber with fuel and air.
In accordance with an other aspect, the improvements provide an acoustic cavity for use in a combustor having a pulsating frequency, the acoustic cavity having a resonator with a fundamental resonance frequency which corresponds to the pulsating frequency of the combustor, the resonator further having an inlet, an outlet, an oscillator for use as a combustion chamber, having the inlet at an acoustic center thereof and defining one end of the resonator, and an exhaust pipe extending from the oscillator and having the outlet at the opposite end of the resonator, the acoustic cavity being CHARACTERIZED IN THAT the oscillator has a fundamental resonance frequency which is an odd harmonic of the pulsating frequency.
In accordance with an other aspect, the improvements provide a combustor having a resonator with a fundamental resonance frequency, the resonator further having an inlet and an outlet, and a combustion chamber opposite the outlet, the combustion chamber defining an oscillator and having the inlet at an acoustic center thereof, the combustor further having an intake system connected to the inlet, the combustor being CHARACTERIZED IN THAT the oscillator has a fundamental resonance frequency which is a harmonic of the resonator fundamental frequency, the intake system is acoustically excitable by the oscillator fundamental frequency, and the intake system defines an acoustic high-pass filter to reflect the resonator fundamental frequency back into the combustion chamber.
In accordance with an other aspect, the improvements provide a method of pulsatingly combusting fuel in a resonator at a fundamental resonance frequency of the resonator, the method comprising: magnifying a harmonic frequency of the fundamental resonance frequency in a combustion chamber portion of the resonator; exciting an acoustic high-pass filter defined by an intake system connected to the combustion chamber with the magnified harmonic frequency; impeding the transmission of the pressure pulses from the fundamental resonance frequency to the intake system with the excited acoustic high-pass filter; and feeding fuel and air into the combustion chamber with the intake system; and periodically increasing the pressure in the combustion chamber by the resonance of the resonator.
In accordance with an other aspect, the improvements provide a combustor having a main longitudinal axis and a pulsating frequency, the combustor comprising: a tubular combustor body having an outlet, a combustion chamber opposite the outlet and an exhaust pipe narrower than the combustion chamber between the combustion chamber and the outlet, the combustion chamber, exhaust pipe and outlet being in flow communication along the main longitudinal axis, and the body having a resonance frequency corresponding to the pulsating frequency; a plurality of substantially longitudinally oriented slots interspaced around the combustion chamber at a longitudinal acoustic center thereof, the slots defining an inlet to the body; and an intake system connected to the combustion chamber inlet.
In accordance with an other aspect, the improvements provide a combustor having an elongated combustion chamber having an inlet proximate a longitudinal center thereof, an intake system connected to the combustion chamber inlet, and a tail pipe extending from the combustion chamber and defining an outlet thereto, wherein the combination of the combustion chamber and the tail pipe define an acoustic resonator having a fundamental resonance frequency at which fuel from the intake system is to be pulsatingly ignited in the combustion chamber, the combustor being CHARACTERIZED IN THAT the inlet comprises a plurality of longitudinally oriented slots being peripherally interspaced around the combustion chamber.
In accordance with an other aspect, the improvements provide a combustor comprising: a tubular combustor body, the body having: a combustion chamber having a plurality of tangentially spaced apertures, and an exhaust pipe narrower than the combustion chamber and extending away from the combustion chamber and being in flow communication therewith, the exhaust pipe defining an outlet of the tubular combustor body; and an intake system connected to the apertures to feed the combustion chamber with fuel and air.
In some cases, the apertures are disposed in a peripheral surface of the combustion chamber. In other cases, the apertures are disposed around an intake tube which protrudes into the combustion chamber.
In accordance with an other aspect, the improvements provide a combustor having a main longitudinal axis comprising: a tubular combustor body having an outlet, a combustion chamber portion opposite the outlet and an exhaust pipe narrower than the combustion chamber between the combustion chamber and the outlet, the combustion chamber portion, exhaust pipe and outlet being disposed along the main longitudinal axis, and the body having a resonance frequency corresponding to a pulsating frequency of the combustor; an intake system having an intake tube longitudinally penetrated into the combustion chamber along the main axis, opposite the outlet, the intake tube having an open end outside the combustion chamber, a closed end inside the combustion chamber, and plurality of longitudinally oriented apertures tangentially interspaced around the intake tube at a longitudinal acoustic center of the combustion chamber, the slots defining an inlet to the combustion chamber.
In accordance with an other aspect, the improvements provide a combustor having an elongated combustion chamber having an inlet proximate a longitudinal center thereof, an intake system connected to the combustion chamber inlet, and an exhaust pipe extending from the combustion chamber and defining an outlet thereto, wherein the combination of the combustion chamber and the tail pipe define an acoustic resonator having a fundamental resonance frequency at which fuel from the intake system is to be pulsatingly ignited in the combustion chamber, the combustor being characterized in that the intake system is aligned on an axis common to the combustion chamber and to the exhaust pipe and that the combustion chamber inlet is peripheral to the combustion chamber.
In accordance with an other aspect, the improvements provide a turbine system for an in-line combustor having an intake system, a body and an outlet aligned along a combustor axis, the turbine system having a power turbine adapted to extract energy from the gasses exhausted from the outlet into rotation, a fan positioned upstream from the intake system, and a shaft connecting the power turbine to the shaft, whereby energy from the exhausted gasses is transmitted from the power turbine to the fan by the rotation of the shaft and the fan thereby enhances the air intake through the intake system.
In accordance with an other aspect, the improvements provide a method of tuning a combustor having a body defining a resonator and a combustion chamber in the body, the method comprising: selecting a combustion chamber shaped to define an oscillator which has a fundamental resonance frequency which is the third harmonic of the resonator fundamental frequency at operation temperature.
In accordance with an other aspect, the improvements provide a method of tuning an ejector having a high frequency fluid nozzle, a first resonant tube and a second resonant tube, the method comprising: selecting a first stage resonant tube which has a fundamental resonance frequency which is a harmonic of the fundamental resonance frequency of the second resonant tube.
In the present specification, when reference is made to a resonant frequency, it is to be understood that what is meant is the resonant frequency during operation, which may depart from resonant frequency at rest due to temperature variations.